Preparation of granulated polymers and copolymers



Patented Aug. 25, 1942 PREPARATION OF GRANULATED POLYLIERS ANDCOPOLYMEBS Gaetano r. DAlelio, Pittsfield, Maia, auignor to GeneralElectric Company, a corporation of New York No Drawing.

Application October 28, 1939,

Serial No. 301,812

14 Claims.

This invention relates to the art of granulating hardenable organicmaterials. More particularly the invention is concerned with certainimprovements and modifications in converting single or mixedpolymerizable solidiflable organic compounds containing the structurefor example single or mixed monomeric or partially polymerized,hardenable organic compounds containing at least one grouping, moreparticularly polymerizable, hardenable aliphatic esters, into granularpolymers or copolymers. This application is a continuationin-part of mycopending application Serial No. 294,498, filed September 12, 1939, andassigned to the same assignee as the present invention.

In the technical utilization of thermoplastic molding materialscomprising thermoplastic polymerized organic substances it iseconomically desirable to have the polymerized body in a finely dividedstate. While this may be accomplished by the mechanical disruption oflarge pieces of polymeric masses, or by solvent precipitation technique,such methods are not completely satisfactory. The former requiresequipment capable of withstanding high mechanical stresses and istime-consuming and expensive, while the latter requires the use ofexpensive solvent-recovery systems to render the process economicallyfeasible. The most satisfactory method comprises initially obtaining thethermoplastic material in the desired granular form.

I have discovered that soluble polymerized unsaturated polycarboxyliccompounds selected from the class consisting of soluble polymeric un-CH=C/ specifically a CHFC/ grouping, from liquid or semi-solid state tosolid,

granular, polymeric modifications capable of direct technicalutilization. Examples of soluble, polymerized, unsaturatedpolycarboxylic compounds which may be used in carrying the presentinvention into effect are soluble, polymeric acids such as ltaconic,fumaric, maleic, mesaconic, citraconic, aconitic, etc., soluble salts ofsuch acids, for example the water-soluble salts such as the alkali-metal(sodium, potassium, lithium, caesium and rubidium) and the ammoniumsalts thereof, and mixtures of such acids and salts. Examples ofpolymerizable, ,hardenable organic compounds, more particularlysolidifiable, polymerizable organic compounds containing a grouping,specifically a om=c grouping, which may be converted into granularpolymers or copolymers ,with the aid of the above-defined polymerizedunsaturated polycarboxylic compounds are polymerizable esters such, forinstance, as polymerizable methyl methacrylate, ethyl methacrylate,methyl acrylate, dimethyl itaconate, etc.', and mixtures of two or moresuch polymerizable esters.

In producing the granular polymers or copolymers in accordance with thisinvention a polymerization. catalyst, for instance an oxygen-liberatingcatalyst such as a super-oxide (examples of which are peroxides of thearomatic acid series, e. g. benzoyl peroxide, etc., aliphatic acylperoxides, e. g. acetyl peroxide, stearyl peroxide, etc.) preferably isincorporated into the material to be granulated. The polymerizable bodycontaining the polymerization catalyst is dispersed, as by rapidstirring, in th dispersion medium (for example water) containing thepolymerized unsaturated polycarboxylic compound in solution state. Thepolymerizable organic compound is caused to be polymerized whilemaintaining it in a dispersed state in the dispersion medium. The solidgranules of polymeric material which form are separated from thedispersion medium by suitable means. The invention is particularlyadapted for the production of granular copolymers, yielding homogeneouscopolymers evenfrom those polymerizable compounds having widely diifercut rates of polymerization. This was quite surprising and unexpected.

I have further discovered that the polymeric unsaturated polycarboxyliccompounds of this invention are best obtained and have greatest uti1-ity as granulating agents when produced by the hydrolysis of polymerizedesters, advantageously alkyl esters, of unsaturated alpha betapolycarboxylic acids. I have found that I can obtain a higher molecularWeight polymerized unsaturated alpha beta polycarboxylic acid by analkaline or an acid hydrolysis of the polymerized alkyl' ation of a saltof the acid or by forming a salt of the directly polymerized acid.Granulating agents prepared by any of these methods may be used informing granular polymers and copolymers, but those derived from thepolymerized esters have a higher granulating efficiency and thereforeare preferred.

A further advantage obtained by using the preferred granulating agentsof this invention in forming granular polymers and copolymers is thatthe granulating effect, for example the particle size and generalappearance of the finished product, can be consider-ably varied, asdesired or as conditions may require (and when other factors are thesame), by varying the extent of hydrolysis of the polymerized ester.Thus, taking polymeric diethyl maleate as an example, I may treat theester with suflicient alcoholic potassium hydroxide to form a polymerichalf ester salt or, by using 2 mols alkali (e. g., sodium hydroxide),the polymeric disodium maleate, as illustrated by the followingequations:

inorganic acids such as sulfuric, hydrochloric,-

phosphoric, etc. The free polymeric acids also I may be prepared bytreating the polymeric monoor di-ester with inorganic acids in thepresence of water. The degree of hydrolysis depends, for example, uponthe mol ratio of the salt-forming compound (alkali, etc.) to thepolymerized ester, or upon the amount of water and inorganic acidavailable during hydrolysis.

The highly polymerized unsaturated alpha beta polycarboxylic acids asthus prepared by hydrolysis of polymerized esters of the acids, or thepolymerized soluble salts of these acids may be purified, if desired,for example by reprecipitation from suitable solvents such as alcohl,acetone, dioxane, etc. Many of these polymerized salts of unsaturatedalpha beta polycarboxylicacids are believed to be new chemicalcompounds.

In order that those skilled in the art better may understand how thepresent invention may be carried into effect, the following illustrativeexamples of the preparation of these new granulating agents and of theirutilization in the production of granular polymers and copolymers aregiven. All parts are by weight.

PREPARATION or GRANULATING AGENTS Example 1 Parts Polymerized dimethylitaconate (finely ground) -Q. 19.8 Potassium hydroxide 7.01 Ethylalcohol (95%) 160.0

The potassium hydroxide was dissolved in the ethyl alcohol, thepolymerized itaconate was added slowly thereto with rapid stirring andthe whole heated and stirred under reflux for 5 hours, at the end ofwhich time a fine powdery material (potassium methyl polyitaconate) hadformed. It was removed from the alcoholic solution by filtration anddried. This mono-potassium salt was completely soluble in water incontrast with the water-insoluble nickel, aluminum, barium, ferric,lead, silver and mercuric salts which also were prepared. Treatment ofthe potassium methyl polyitaconate (polymerized potassium methyl esterof itaconic acid) with an equal molar quantity of hydrogen chlorideyielded a mono-methyl ester of polyitaconic acid which was insoluble inwater but soluble in alcohol (95%) and in dilute sodium hydroxidesolutions.

The above components were heated and stirred under reflux for 6 hours,first forming a solution of the potassium hydroxide as described underExample 1 before adding the polymerized itaconate thereto and refluxingthe whole. A reaction product comprising the dipotassium salt ofpolymerized itaconic acid was obtained by evaporation of the solvent andwashing with alcohol to purify the salt. The polyitaconic acid obtainedby treating this di-salt with inorganic acids was insoluble in water butreadily soluble in dilute alkali solutions.

Example 3 Parts Polymerized dimethyl fumarate 17. 2 Potassium hydroxide14. 0 Ethyl alcohol 160. 0

were treated in a manner'similar to that described under Examples 1 and2. The dipotassium polyfumarate thus obtained was soluble in water.Polymeric fumaric acid, vfiinsoluble in water, was prepared byacidifying an aqueous solution of the di-salt with mineral acids.

Example 4 Parts Polymerized dimethyl fumarate 20 Sulfuric acid(approximately 98%) 4 Water were refluxed with stirring for 24 hours.The

' with stirring.

Mono-potassium methyl polyitaconate of Example 1 0.25

were mixed and heated at 85 C. for 3 hours Beads of polymerized methylmethacrylate about 1 to 2 mm. in diameter were filtered from the aqueousvehicle anddried for 3 hours at 55 C. These beads or granules wereeasily molded at 140 C. under a pressure of 4000 pounds per square inchfor 5 minutes, yielding clear, hard molded articles of good surfaceappearance.

Example 6 Parts Monomeric methyl methacrylate 25.0 Benzoyl peroxide(dissolved in the above) 0.25 Water 100.0 Dipotassium polyitaconate ofExample 2 0.25

were treated in essentially the same manner as described under Example 5to obtain white, polymeric, non-spherical granules of irregular shape.The molded articles were similar in appearance and moldingcharacteristics to those made from the granules of Example 5.

Example 7 Parts Monomeric ethyl methacrylates 20.0 Monomeric dimethylitaconate 10.0 Benzoyl peroxide (dissolved in the above)- 0.3

Water 130.0 Polymerized itaconic acid in an aqueous alkaline solution of0.3 part sodium hy droxide in 10 parts water"-.. 0.3

of about 4000 pounds per square inch. The

molded articles were clear, hard and of good surface finish.

Example 8 Parts Monomeric ethyl methacrylate 21.0 Monomeric dimethylitaconate 9.0 Monomeric diallyl itaconate 0.3 Benzoyl peroxide(dissolved in the above)- 0.6

Water 150.0 Disodium polyitaconate (polymerized disodium itaconate) 0.3

were mixed and the polymerizable materials copolymerized by heating themixture at 85 to 90 C. for two hours with stirring. Twenty-five parts ofsmall, clear, colorless beads or granules of the copolymer were obtainedby filtration of the above solution at the end of the polymerizationperiod. Clear, hard, molded articles were produced by molding the driedheads at suitable elevated temperatures and pressures, for example at130 to 150 C. and at pressures of the order of 4000 to 6000 pounds persquare inch.

Example .9

Same formula and essentially the same technique were followed in makinggranular copolymers and molded articles therefrom as described underExample 8 with the exception that the granulating agent comprised 0.3part of polymerized itaconic acid in an aqueous alkaline solution of 0.3part sodium hydroxide in 10 parts water. The polymerized itaconic acidwas obtained by acidifying the polymerized dipotassium itaconate(dipotassium polyitaconate) of Example 2 with sulfuric acid andthereafter washing the mass with a suitable solvent to remove excessacid and sodium sulfate. The ethyl methacrylate-dimethylitaconate-diallyl itaconate interpolymer .was obtained in the form ofglass-clear granules.

Example 10 Parts Monomeric ethyl methacrylate 17.0 Monomeric dimethylitaconate 13.0 Benzoyl peroxide (dissolved in the above)- 0.3

Water 130.0 Dipotassium polyfumarate (polymerized dipotassium fumarate)of Example 3 0.3

were mixed and the polymerizable materials copolymerized by heatingand-stirring for 5 hours at to C. Glass-clear beads having a digrouping,in a dispersionmedium in which the granulating agent is soluble and thepolymerizable organic compound is substantially insoluble Water is anexample of a. suitable dispersion medium in which the polymerizableorganic compound advantageously may be dispersed. Water is preferred asthe disperson medium for obvious economic reasons, although it will beapparent to those skilled in the art that numerous other dispersionmediums may be employed, the choice depending upon the initial cost andthe solubility of the granulating agent and the insolubility of thepolymerizable and the polymerized organic compound therein. The actionof these. granulating agents in increasing the stability of thedispersed-organic compound until solid polymers are formed appears to beanalogous to that ofan emulsifying agent in protecting an emulsion.

The size and shape of the granulated polymerized organic compounddepends: for example, upon such influencing variables as theconcentration of the granulating agent, the concentration of thedispersion medium, the .purity of the granulating agent, the speed ofstirring, the solubility and other characteristics of the polymerizableand the polymerized organic compound, the pH of the mixture, whether thepolymerized body is a homogeneous compound (a polymer) or aheterogeneous compound (a copolymer) and the solubility in thedispersion medium and the other characteristics of the particulargranulating agent employed.

The granules of the polymerized organic compound may be separated fromthe dispersion medium by filtration, centrifuging, etc., and fur-' therdried, if necessary, by suitable means. The dried granules may be moldeddirectly or they may be sheeted first and then molded. They also may bedissolved in suitable solvents and the resulting liquid compositionsused as surface coating materials. The dried beads also may be used tosurface a base member. In such applications they serve as focal pointsfor light reflection. Sheet materials such as paper, cloth, etc., whenfaced on one or both sides with the resin granules likewise may becompressed under heat suflicient to cause the resin to flow and to forma smooth or embossed surface finish.

The granulating agent may be recovered from the dispersion medium andmay be re-used. Or, the dispersion medium (e. g., a dispersion mediumcomprising water) containing the ranulating agent may be recovered andre-used, adding if necessary, additional granulating agent to therecovered solution to provide a dispersion medium containing the desiredconcentration of granulating agent.

It will be apparent to those skilled in the art that this invention isnot limited to the granulation of the particular organic materialsmentioned in the above illustrative examples and that numerous otherpolymerizable, hardenable organic compounds similarly may be granulated.Additional examples of compounds that may be granulated with the aid ofthe granulating agents herein described are monomeric or partiallypolymerized diethyl itaconate, diallyl itaconate, ethyl acrylate, methylethacrylate, vinyl compounds such as vinyl acetate, etc., and mixturesof these and other polymerizable organic compounds such, for example, asmixtures of polymerizable diethyl itaconate and methyl methacrylate,vinyl acetate and methyl methacrylate, ethyl acrylate and ethylmethacrylate, methyl acrylate and glycol dimethacrylate, styrene andpropyl methacrylate, etc. In general, anynormally flowable, hardenable,polymerizable organic compound containing a CH=C grouping, specificallya CH2=C grouping, that is capable of being dispersed in a dispersionmedium in which the granulating agents of this invention are wholly orpartly soluble, and which in the chosen medium can be polymerized (withor without a polymerization catalyst) to a solid state, can be convertedinto solid granules of varying particle size and shape with the aid ofthese new granulating agents.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of converting a polymerizable, hardenable mass comprisinga polymerizable, hardenable aliphatic ester into a granular polymericmodification which comprises dispersing said mass in a dispersion mediumcomprising water in which the said mass is insoluble, said dispersionmedium containing a granulating agent soluble therein, said agentcomprising a soluble polymerized unsaturated polycarboxylic compoundselected from the class consisting of soluble polymeric unsaturatedalpha beta polycarboxylic acids, soluble salts thereof, and mixtures ofsuch acids and salts, and causing the said polymerizable mass to bepolymerized while maintaining the same in a dispersed state in the saiddispersion medium.

2. The method of converting a polymerizable, hardenable mass comprisinga polymerizable, hardenable aliphatic ester into a granulated polymericmodification which comprises incorporating into the said mass apolymerization catalyst, dispersing the resulting mass in a dispersionmedium comprising water containing a water-soluble salt of' a polymericunsaturated alpha beta polycarboxylic acid, polymerizing the said mass,and maintaining the said polymerizable mass in a dispersed state in thesaid dispersion medium during polymerization.

3. A method as in claim 1 wherein the granulating agent comprises analkali-metal salt of a polymeric unsaturated alpha beta polycarboxylicacid. I

4. A method as in claim 1 wherein the granulating agent comprises apolymerized alkalimetal salt of itaconic acid.

5. A method as in claim 2 wherein the watersoluble salt of a polymericunsaturated alpha beta polycarboxylic acid is a water-soluble ,salt ofpolymeric itaconic acid.

6. The method of converting a polymerizable, hardenable mass comprisingan ester of methacrylic acid into a granulated polymeric modiiicationwhich comprises dispersing the said mass in a dispersion mediumcomprising water containing a water-soluble salt of a polymericunsaturated alpha beta polycarboxylic acid, polymerizing the said mass,and maintaining the said mass in a dispersed state in the saiddispersion medium during polymerization.

7. A method as in claim 6 wherein the ester of methacrylic acid ismethyl methacrylate.

8. A method as in claim 1 wherein the granulating agent comprises apolymerized alkalimetal salt of maleic acid.

9. A method as in claim 1 wherein the granulating agent comprises apolymerized alkalimetal salt of fumaric acid.

10. A method as in claim 2 wherein water.- soluble salt ofa polymericunsaturated alpha beta polycarboxylic acid is awater-soluble salt ofpolymeric maleic acid.

11. A method as in claim 2 wherein the watersoluble salt of a polymericunsaturated alpha beta polycarboxylic acid is a water-soluble salt of apolymeric fumaric acid.

12. The method of converting a polymerizable, hardenable mass comprisingan ester of acrylic acid into a granulated polymeric modification whichcomprises dispersing the said mass in a dispersion medium comprisingwater'containing awater-soluble salt of a polymeric unsaturated alphabeta polycarboxylic acid, polymerizing the said mass, and maintainingthe said mass in a.

dispersed state in the said dispersion medium during polymerization.

-13. The method of converting a polymerizable, hardenable masscomprising avinyl ester into a granulated polymeric modification whichcomprises dispersing the said mass in a dispersion medium comprisingwater containing a watersoluble salt of a polymeric unsaturated alphabeta polycarboxylic acid, polymerizing the said mass, and maintainingthe said mass in a dispersed state in the said dispersion medium duringpolymerization.

14. The method of converting a polymerizable, hardenable mass comprisingvinyl acetate into a granular polymeric modification which comprisesincorporating into the said mass a peroxide polymerization catalyst,dispersing the resulting mass in a dispersion medium comprising watercontaining a polymerized alkali-metal salt of an unsaturated alpha betapolycarboxylic acid, polymerizing the said mass, and maintaining thesaid polymerizable mass in a dispersed state in the said dispersionmedium during polymerization.

GAETANO F. DAIELIO.

